German Offenlegungsschrift No. 2532504 discloses a personal security and surveyance or monitoring arrangement in which the person to be surveyed has a mobile transmitter which sends out an alarm signal which is received at a central control point and there sets off an alarm. When a central control point is to be used for a plurality of transmitters there is a danger that there could be interference between the alarm signals sent out from the different transmitters, and it is not possible to have an unambiguous co-ordination with a particular transmitter of an alarm signal received at the central control point. Moreover this arrangement and the signal transmission is not continuously supervised as regards its functioning capacity, whereby a troublefree reliable operation is not ensured.
German Offenlegungsschrift No. 2531664 discloses a circuit arrangement for signal safety, that is to say for supervising the functioning in the transmission of a signal. In this circuitry a neutral signal of a specific form is transmitted to the receiver during a rest condition, particularly on an occasion when no alarm signal is transmitted, and this neutral signal is switched off when any interference or alarm occurs, and in this event a signal of different form is sent out. In this case there is certainly a continuous supervision of the functioning of the transmitters and the signal transmission, but the neutral signal which is continuously transmitted consumes a relatively large amount of energy, so that this arrangement is not suitable for mobile transmitters which for example are used in personal security units, in which cases small and light transmitter units with small batteries or accumulators are important. Apart from the energy-consumption considerations the continuously transmitted signals when a plurality of transmitters are in use would cause mutual interference, and consequently a safe and reliable supervision of the functioning of an arrangement which includes a plurality of transmitters would not be possible.
The present invention is based on the object of affording a method and providing arrangements which cater for the transmission of different information signals between a plurality of transmitters and a receiver station on one transmission channel.